Research will continue along two main avenues: plant research, and research on a mammalian in vivo system, the Chinese hamster cheek pouch. The plant research will focus on two problems: (1) Analysis on root meristem cells to determine the extent of perturbations to specific parts of the cell cycle will continue. In particular, the S phase or DNA synthetic period will be examined using methods developed in the past year. (2) Studies using the focused transducer to sonicate small root sections will continue. Roots of Vicia faba will be sonicated at the meristem (first millimeter) and behind the meristem, after which the meristem cells will be examined for the presence or absence of chromosomal anomalies. The studies on mammalian tissues will use the Chinese hamster cheek pouch. The cheek pouch offers many of the advantages of plant roots since it can be exteriorized and sonicated under conditions of controlled temperature and accurate dosimetry. The specific endpoints to be examined initially will include mitotix index, labelling index, and chromosomal morphology of epithelial cells. Ultrasound frequencies and intensities employed will be similar to those employed in our studies of plant roots and cultured cells (approximately 1-2 MHz, 1-30 W/cm2).